The present invention generally relates to an improvement for paint spray booths and, more particularly, is concerned with a spray booth designed to minimize air supply volume flow requirements while at the same time minimizing overspray buildup in the vicinity of critical apparatus located within the booth.
Paint spray booths are typically found in production lines for products such as automobiles. Parts of the automobile body which must be painted are conveyed into an enclosed booth and the desired paint is applied by spraying the paint either at preselected locations via specially designed apparatus, manually by human operators, or through the use of robotics.
Much of the paint emitted from the spray apparatus never reaches the part being painted, but appears as overspray in the booth's atmosphere. This overspray must be removed from the booth for a variety of reasons. It cannot be allowed to fall back on the painted body or the interior of the booth. Removal of the overspray is best accomplished if the booth is provided with a laminar air flow with sufficient air velocity to provide an exhaust stream for carrying the overspray along with it. In a conventional booth, the air enters a booth through a perforated ceiling, usually comprised of a wire mesh and flows down through a perforated floor, usually steel grating, thereby creating a constant down draft. In many conventional booth systems, downward draft exhaust air carries the overspray through the floor where it mixes with water to be disposed of as sludge.
Since paint spray booths can be hundreds of feet long with many work stations along the way, it is desirable to be able to apply different coats of paint to the parts as they pass through the booth. Cross contamination should be avoided by preventing the paint at each work station from drifting through the overspray to the next work station.
Temperature and humidity conditions in the booth must also be monitored very closely. Certain paints, for instance, require very accurate controls at these two variables.
Another concern of paint spray booths is emissions into the atmosphere. In order to reduce the concentration of paint particles in the air exhausted to the environment, the air leaving the floor of the paint spray booth must be cleaned.
Removing overspray, controlling air temperature and humidity and cleaning paint particles from the exhaust air requires large amounts of operating energy. The energy requirements can be very expensive, and therefore reducing the energy required for each of the aforementioned concerns and lowering capital investment for related equipment can be accomplished by minimizing the total required air volume flow rate inside a paint spray booth at each work station.
One prior approach to minimizing the required air volume flow rate is set forth in U.S. Pat. No. 4,932,316 wherein a paint spray booth is provided with movable inner walls which can be placed around a workstation in such a way as to allow room for the work to be accomplished, while keeping the total area of the workstation wherein the exhaust air must flow at a minimum. The inner walls are constructed of a light weight material which would allow for easy manual placement inside the booth. However, it has been found that a booth with movable walls which extend from the ceiling of the booth all the way to the floor may allow for unacceptable overspray buildup in the area of the spray applicators, especially in electrostatic paint sprayer applications. Where the movable walls extend for the full heighth between ceiling and floor of the booth, the spray applicator would be totally within the application area, thus subjecting itself to undesirable buildup, especially in an electrostatically charged particle environment.